THE ALL DIGITAL PHOTOGRAMMETRIC WORKFLOW:
REDUNDANCY AND ROBUSTNESS
Michael Gruber?, Roland Perko?, Martin Ponticelli*
* Vexcel Imaging GmbH, Münzgrabenstrasse 11, 8010 Graz, Austria — [mgruber, mponti]@vexcel.co.at
"Institute for Computer Graphics and Vision, Graz University of Technology,
Inffeldgasse 16, 8010 Graz, Austria - perko@icg.tu-graz.ac.at
Commission I, WG 1/6
KEY WORDS: Digital Camera, Quality Assessment, Analog Film
ABSTRACT:
Digital aerial cameras, among them the UltraCam D, the new large-format digital aerial camera of Vexcel Imaging, are ready to
replace the aerial film camera. This is reason enough to highlight the improvements in radiometric and geometric quality that such a
camera provides. Is it the ability to resolve dark shadows, is it the ability to simultaneously register panchromatic, true color and
false color infrared or is it the ability to increase the forward overlap at no extra costs for film, development and scanning, we are
convinced, that with such digital cameras, a novel strategy of source image acquisition can be considered.
Aerial photogrammetry has long used a convention of 6095 forward overlap and 20% sidelap, in order to provide for stereo
compilation and the generation of products such as digital terrain models (DTM) and orthophotos.We argue that digital cameras can
be used to challenge standard photogrammetric conventions: no longer is film grain an issue, high radiometric resolution at a 12 bit
level and no longer is the number of images the predominant driver in defining a photogrammetric project. Increased redundancy
and higher overlaps provide a key to optimized levels of accuracy, automation and robustness in a production environment.
The design of the UltraCamD with its parallel architecture permits a very high framing rate, thus affording flexibility to select a
forward overlap of up to 90%. Further, the role of parallel architecture in sensor design, together with efficient data transfer and
storage options, is discussed. If this change in the strategy of image acquisition take place, an enhancement of automation and
robustness in the photogrammetric production can be expected.
I. INTRODUCTION
The replacement of the aerial film camera obviously started in
July 2000 with the product announcements of the ADS-40 by
LH-Systems (now Leica Geosystems) and of the DMC by Z/I
Imaging. In May 2003 the UltraCamD was introduced. This is a
90 Mpixel large format aerial camera by Vexcel Imaging with a
focus on a one-on-one replacement of aerial film cameras. This
is achieved by the use of an unchanged work flow, based on the
well known frame image.
The initial economic advantages can obviously be detected in
the smooth all-digital operation and in the reduction of expenses
when costs for film, film development and scanning can be
ignored.
Beyond these initial advantages the all digital photogrammetric
workflow offers numerous opportunities for improving the
current state-of-affairs of photogrammetry as much so that one
could speak about a "paradigm shift". The most important
opportunity is the ability to dramatically increase the forward
overlaps in photogrammetric surveys without any added cost,
and producing a much higher level of automation in
photogrammetric data analysis. Photogrammetric software will
have to be adjusted to go from current stereo, thus "2-ray
photogrammetry” towards “multi-ray” solutions.
Beside this “multy-ray” concept the ability of such digital aerial
camera to simultaneously register panchromatic light at high
geometric resolution, true color red-green-blue and false color
infrared light offers new opportunities in photogrammetric color
sensing.
2. THE ULTRACAM, DIGITAL CAMERA
2.1 DESIGN ISSUES
The sensor unit of Vexcel's UltraCamD consists of eight
independent cameras, so-called cones. Four of them create the
large format panchromatic image at a size of 11500 by 7500
pixels. The other four cones are responsible for the multi
spectral channels of the UltraCamD, i.e. red, green blue and
near infrared (Figure 1).
The panchromatic part of the camera combines a set of 9
medium format CCD sensors into a large format panchromatic
image. The multispectral channels are supported by four
additional CCD sensors.
Fig. 1: UltraCamD Sensor Unit and Storage/Computing Unit
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